Neither of us are lawyers, but my amateur knowledge
suggests that you are mistaken.

Under US law the author holds copyright on anything that
they write unless they don't for contractual reasons -
see works for hire. However copyright is a limited form of
ownership.

For instance once you have created and sold a copy, you
cannot control the further sales of that copy, or say that
certain people cannot own that copy. This is why used
bookstores can resell books. (Publishers tried to stop
that and failed.) This also covers your ex. However if
your ex decided to make copies of your personal letters
and send them to friends ridiculing you, then you have a
copyright claim against your ex.

Similarly I would be shocked and astonished if mere
possession of the physical article of a letter from Ernest
Hemingway gave you any right to publish it in your book of
letters. This runs counter to everything that I have ever
heard on the topic, and before you consider doing something
like that, please discuss it with a lawyer! (One of the
notable early copyright cases involved the inclusions of
letters from Alexander Pope without his permission.)

As for the SSSCA, it is now renamed the CBDTPA, and makes
half-hearted attempts to address the problems above. What
they are coming up with is completely technically
unworkable, but now the trick is explaining this to
non-technical people who are busy and have no understanding
of what the implications of their "small spec change" will
be. (Gee, where have we seen this before?) At least they
also have realized the potential to create a monopoly
position from trying to make it work, and have addressed
that. (They also no longer get support from Microsoft for
the bill - fancy that.)